Scientists want to know if exposure to PFAS, a toxic class of chemicals, can contribute to severe illness from COVID-19 or reduce the effectiveness of vaccines. Known as forever chemicals because they don’t naturally break down in the environment, PFAS can cause serious health problems, including effects on the immune system. PFAS — which stands for per- and polyfluoroalkyl substances — are widely used in consumer products such as nonstick cookware, flame-retardant fabrics, and some food packaging. They are also found in firefighting foam used at airports and current and decommissioned military bases, such as those in Bucks and Montgomery counties in Pennsylvania and at Joint Base McGuire-Dix-Lakehurst in New Jersey and Dover Air Base in Delaware. To read the full story.